Training Guide: Programming in HTML5 with JavaScript and CSS3 Ebook

66 CHAPTER 3 Getting started with JavaScript

Lesson 1: Introducing JavaScript

This lesson presents a great deal of the JavaScript language. Although much of the con-

tent exists in previous releases of JavaScript, all content in this chapter is part of the latest

JavaScript specification.

After this lesson, you will be able to:

■■Define JavaScript variables.

■■Create JavaScript statements.

■■Create function declarations.

■■Create function expressions.

■■Convert objects to a different type.

■■Write conditional statements.

■■Write looping statements.

■■Handle errors.

Estimated lesson time: 60 minutes

Understanding JavaScript

JavaScript is not related to Java, although it is a curly-brace language like Java, C#, C++, and

many other programming languages. JavaScript is related to ECMAScript, however. Ecma

International, working with other organizations, created this standardized scripting language

in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side

scripting on the web, and you commonly see several well-known variations of ECMAScript

such as JavaScript, JScript, and ActionScript. The current release is ECMAScript Edition 5.1 and

most common browsers support ECMAScript Edition 5.0 or newer.

JavaScript is untyped, which means that when you create a variable, you don’t need to

specify its type. This might seem like a feature because you declare a variable with the var

keyword and assign a string to the variable, and later, you can assign a number to the same

variable. However, it’s difficult to apply Microsoft IntelliSense to untyped languages. It’s also

difficult to maintain the code because it’s difficult to know the variable’s type. This might

cause you to develop an immediate dislike for the language, but persevere and work with the

language. You’ll be amazed at the power of JavaScript. Although you might never want to

trade in Visual Basic .NET or C#, you’ll find that the more time you spend with JavaScript, the

more respect you’ll develop for this language.

One way to ease the pain of learning JavaScript is to make sure you are using tools that

can help you. The latest release of Visual Studio 2012 adds more IntelliSense to JavaScript and